The faint clicking sound was repeated. Beads of perspiration stood upon M. Max's forehead; his imagination had been running away with him. God! this was a house of fear! He controlled himself, but only by dint of a tremendous effort of will. Stealthily watching the lamp, he saw that the arc described by its gyrations was diminishing with each successive swing, and, as he watched, its movements grew slighter and slighter, until finally it became quite stationary again, floating, purple and motionless, upon the stagnant air. Very slowly, he ventured to change his position, for his long ordeal was beginning to induce cramp. The faint creaking of the metal bunk seemed, in the dead stillness and to his highly-tensed senses, like the rattling of castanets. For ten minutes he lay in his new position; then moved slightly again and waited for fully three-quarters of an hour. Nothing happened, and he now determined to proceed with his inquiries. Sitting upon the edge of the bunk, he looked about him, first directing his attention to that portion of the wall immediately above. So cunningly was the trap contrived that he could find no trace of its existence. Carefully balancing himself upon the rails on either side of the bunk, he stood up, and peered closely about that part of the wall from which the sound had seemed to come. He even ran his fingers lightly over the paper, up as high as he could reach; but not the slightest crevice was perceptible. He began to doubt the evidence of his own senses. Unless his accursed imagination had been playing him tricks, a trap of some kind had been opened above his head and someone had looked in at him; yet--and his fingers were trained to such work--he was prepared to swear that the surface of the Chinese paper covering the wall was perfectly continuous. He drummed upon it lightly with his finger-tips, here and there over the surface above the bed. And in this fashion he became enlightened. A portion, roughly a foot in height and two feet long, yielded a slightly different note to his drumming; whereby he knew that that part of the paper was not ATTACHED to the wall. He perceived the truth. The trap, when closed, fitted flush with the back of the wall-paper, and this paper (although when pasted upon the walls it showed no evidence of the fact) must be TRANSPARENT. From some dark place beyond, it was possible to peer in THROUGH the rectangular patch of paper as through a window, at the occupant of the bunk below, upon whom the shaded lamp directly poured its rays!